1. Field Of The Invention
The invention relates generally to devices and methods employed to prevent the accidental implantation of surgical implements used in the course of a surgical procedure. More specifically, the invention employs an active surgical implement tagging and detection system, adapted to sense the presence of retained implements before post-operative suturing takes place.
2. Description Of The Prior Art
Known prior art devices and methods used to detect retained surgical implements can generally be classified as "passive" in nature. For example, X-ray examination has long been advocated as a useful means to detect the presence and location of radio opaque implements and radio opaque tags or thread attached to surgical sponges and gauze, or the like. Representative art disclosing such an approach is U.S. Pat. No. 2,698,270 issued to Mesek and U.S. Pat. No. 3,698,393 granted to Stone. X-ray examination of patients does provide fairly reliable screening for retaining articles. However, each screening requires the cumbersome task of moving the X-ray machine into place over a properly positioned patient, whose wound has already been sutured to avoid sterility problems. In the event that a retained implement is discovered, it is necessary to reopen the wound, remove the implement, and then resuture the wound before the patient can be released from anesthesia. In view of the foregoing, X-ray examination for retained surgical implements has not proved practical as a regular procedure.
Other passive systems proposed preferably use a hand manipulable detector to sense the presence of metal, magnetized particles, or radioactive material attached to or associated with the surgical implements. Prior art from among this group includes U.S. Pat. Nos. 3,097,649; 3,422,816; and 3,587,583. While this approach allows examination of the patient in the operating room, health hazards are posed by the radioactive material, and the extraneous metal and magnetic responses present in the operating room make the other systems less than completely reliable.
More recently, in U.S. Pat. Nos. 4,114,601 and 4,193,405, Abels teaches the tagging of surgical implements with a small film deposition of ferrite or other semiconductor material exhibiting gyromagnetic resonance at selected frequencies. When exposed to electromagnetic radiation at two selected frequencies, a higher order product frequency is radiated and detected by an RF receiver. While the Abels device is claimed to work at any frequency, the proposed range of frequencies discussed in the patents is 4.5-5 Gigahertz. It is well recognized that human tissue is significantly absorptive of radio frequency energy at this microwave frequency, and even the 0.5 watt transmitter power range proposed in Abels could present a health hazard either to the patient or to the administrator of the test.
Consequently, while the "passive" approach is initially appealing in terms of the simplicity and the diminutive size of the surgical implement tag or identifier, other problems are posed by the cost, safety and reliability of the transmission and detection systems used to sense the presence of passive tags.